Answer. Already I have shown you that the S'firot are the head and beginning of all that comes within the limits [of the universe], and all that comes within the limits is defined by its substance and its space - and there's no substance without a space, and there's no space without the concept of substance. And there's nothing that can reduce the substance of a force that does't have length, width, or depth.
These are 9, and accordingly there's no substance established without a space for it, and there's no space established without the force of the substance. There's no number complete in substance and in place lower than 10, and therefore its called 10 (Eser) and not 9, 10 and not 11, because like the that 3 goes into 9, so the fourth is space. God's judgement is that they should be 10 to hint that at the space from the force of substance, and substance only has one force.